Mounting unit for phonograph tone-arms



y 1950 E. o. THOMPSON 2,506,692

MOUNTING UNIT FOR PHONOGRAPH TONE-ARMS Filed Oct. 11, 1947 K INVENTOR.lulllllllmmw L /W5? 0 190M 10 BY F/GZ 2. 63, Q 4 %,,,,M I f Adi/V7)Patented May 9, 1950 UNITED STATES PATENT QFFICE MOUNTING UNIT FORPHONOGRAPH TONE-ARMS 4 Claims. 1

The present invention relates to phonograph apparatus and, particularly,to phonograph apparatus of the type having a pivotally mounted tone-armadapted for playing engagement with a record supported on a turntable.Specifically, the invention has to do with improvements in the mountingof the tone-arm.

In phonograph apparatus of the type above mentioned, the tone-arm whichcarries the pickup, is customarily mounted to swing freely in adirection transverse to the record supporting surface of the turntable,so that the pick-up needle can be brought in and out of engagement withthe playing surface of the record, and so that the tone-arm will be freeto move with undulations of the record. The tone-arm is also mounted toswing in a direction paralleling said surface of the turntable, so thatthe tone-arm can be moved out of the playing field to allow changing ofrecords, and so that the pick-up needle will be free to track the recordgroove. Because the tone-arm is free to pivot in the two above mentioneddirections, sudden translatory or rotatory movements of the phonographresult in undue displacements of the tone-arm and cause the pick-upneedle to jump oil or slide across the record. For these reasons,ordinary phonographs are adapted to play properly only when in a stableand substantially level position. They are not suited to play while intransportation, and are particularly incapable of adequately playing indriven vehicles, such as automobiles, which are subject to shocks, jars,and vibrations due to abrupt stopping and starting, traveling up anddown hills and over bumps, and changing direction from a straight linepath into a curve or turn.

It is, therefore, the primary object of this invention to provide aphonograph which is adapted to play in any position and which can playproperly in transportation, particularly, in moving vehicles. To thatend, the invention employs a tone-arm mounting which allows the tone-armto be pivotally moved about two perpendicularly related axes but whicheffectively prevents accidental displacement of the tone-arm about saidaxes and, thus, insures positive retention of the pick-up needle in therecord groove, even when the phonograph is subjected to severe jolts.

Another object of the invention is to provide a tone-arm mounting whichmakes the above mentioned advantages possible, and which has asimplified construction capable of being readily associated with otherexisting parts of the phonograph without necessitating material changestherein. This object of the invention is obtained by means of a unitarystructure which is adapted to provide for normal swinging movements ofthe tone-arm but which functions to counteract any tendency of thetone-arm to move abnormally under influence of shocks, jolts, jars orunusual severe movements of the phonograph.

Still another and more specific object of the invention resides in theprovision of a tone-arm mounting arrangement which makes it possible tobalance the tone-arm both statically and dynamically so that the pick-upneedle will not slide across nor leave the surface of the record duringthe playing thereof, even should the: phonograph be subjected to unusualshaking or swinging motions in any direction. For that purpose, theinvention provides a tone-arm supporting unit in which counterbalancingand counterrotating means, having moments of inertia dynamicallybalancing those of the tone-arm assembly, are so coupled to saidassembly that said moments of inertia oppose undesired movements of thetone-arm assembly.

These and other objects of the invention, and the manner in which theyare obtained, will be fully understood from the following description.based on the accompanying drawing which illustrates a preferredembodiment of the invention, and in which:

Figure l is a side elevational view showing a tone-arm mountingconstructed in accordance with the invention, certain parts being brokenaway for clarity of illustration;

Figure 2 is an enlarged elevational-sectional view looking in thegeneral direction of arrows 2--2 of Figure 1; and

Figure 3 is an exploded view of certain parts of the arrangement asshown in Figure 1, and illustrates the mode of assembling the tone-armmounting unit with the phonograph base plate and tone-arm.

With more particular reference to the drawing, Figure 1 shows aturntable 5 and a tone-arm 5. The turntable is conveniently mounted on abase plate 1, and is adapted to be rotated in the usual manner by meansof a suitable motor (not shown). The turntable is further adapted tosupport a record, as is indicated at 8, and to rotate the record inrelation to the tone-arm 6. The tone-arm carries a pick-up 9 which isprovided with a needle Ill disposed for engagement with the customaryspiral modulated groove of the record. As shown, tone-arm 6 is supportedto swing about two perpendicularly related axes. Swinging movement ofthe tone-arm about one of said axes base plate.

3 allows for movement of said tone-arm in a direc tion transverse to theplane of the turntable, in order that the pick-up needle may be broughtin or out of engagement with the record, and in order that the tone-armmay accommodate it self to undulations of the record. Swingingmovementofthe-gtone-arm abeut the other 'ofgsaid axes allows formovement of said tone-arm in a direction generally parallel to the planeof the turntable, in order that said tone-arm may be;

moved out of and into the playing field and in order that the pick-upneedle may follow the} record groove, unobstructedly.

In accordance with the inventioneandiaslillusl entirety, by thereference numeraL U, and, which.

is constructed and arranged to provide for movement of the tone-arm inthe two above named'idirections. For that purpose, unit ll includes agenerally cylindrical supporting member; 'or standard 1 2 .'which; asmore clearly shown,- in ;Figure;2;.has ears l3gadapted toprovide-diametrically opposed: bearings l4; These bearings. may be; ofan-y. suitable construction, and are adapted to, receive. a rotatableshaft or pivot. l5. Ascan best be seen in said Figure 2; the: sides of:the tome-armv 6-. are; provided: with bifurcatedtrunnions;l-fiswhich.are-adapted-to engage pivot I Stand. tobe rigidlyconnected thereto, as by means-of suitable: locking elements- L1. Thus;the tonearm can; beswungatiright; angle: to-the longitudipal; axis: of;the mainsupporting member l-2-. 'Iihge member I2" is arranged; forrotation, about its; longitudinal; axis, on the, base plate- 'l. This isconveniently accomplishedby providing aballbearingconnection which;as=more clearly shown inEigureaZ is mounted on member Mandhas-a part IIflradapted to be fixedly-secured t: the base plate. For; that purpose,-the member l2; to,-

gethen' with; its; ball-bearing; connection;. isreceivedjinan opening19in the-base plate, andi-the part I8 of the ball-bearing connection hasa;;1ip 20 disposed to; bear on, the one side of the base plates The partl8 further-has a threaded per.- tion' 2-! in engagement with anut- 22:adaptedzfor bearing engagement, with the, other side of the In thismanner; thetone-arm isiree to rotate with member I2 abouttheflongitudinal axis ofthe latter. As.i1lustrated;in= Figure 1-; a rcoil spring-23, which has oneorits endsattached to a connection: 24'. onthe toneearm, and which has its other end attached to-a'brackett25;secured,

asrbyvmeans oi-jfastening; element 28, on; a; rotatable} member; 12;serv s. -t ma ntain; he-.- pi k-up needle in proper trackingengagement-with; the recordigroovet As. hereinbefore stated the,tone-arm, accord ing toithe presentjinvention is adapted to-be-perfectlybalanced-statically and; dynamically about both of its axes of rotationso as not; tobedeleteriously afiected by shocksorvibrations to whichthe-phonographmay besubjected. For that-purpose; andas particularlyshown in E ure; 1,. the toneearm' s provided; w h: an d p r ion:whichprojectsbeyond theipivot; l5, and acoun terbalancing weight 28 is:attached to this ex tended; portion. 'l lhe -massot Weight 28.- and. ofthe extendedportionjl onone side of thepivotal axes-issuchthatitaccurately-balancesthe mass ofqthepick upandof the tone-armportionon the otherside; of said; axesi, Because; of this. con:

struction, it: will be understood that; in eife t; the

tonerarm assembly; iszpiuoted: for rotation: at; its Center. of gravity;so; that, the toner-arm... when; at

rest, is perfectly balanced. In order to allow for critical adjustmentin balancing the tone-arm, the weight 28 is adjustably mounted on thetonearm portion 21. This is conveniently accomplished by providing saidportion with a slot 29, and by providing the weight with a suitablereleasable-locking element 36:. passing through said slot.Afterloosening element 3%, the: weight may be slidably adjusted untilperfect balance is secured, and then the weight may be retained inadjustedpositiomby tightening said element.

Because the tone-arm is perfectly balanced in the manner abovedescribed, translatory movementsro-ithe phonograph in directionstransverse to either therotatable member i2 or to the rotatable pivotl5', will not deleteriously affect the inertia. of, the tone-arm.Accordingly, the tonearm, if moving under influence of the radialleadforce-developed by the spiral groove of the record, will tend tocontinue its normal movement, although thephonograph mfiyrbe subjectedtoseverejolting in directionstransverse to the pivotalaXes-of thetone-arm;

However, the-inertia ofthe balanced tone-arm would be deleteriouslyaffected by unusual-rotatory movements; ofthe phonograph in; directionscorresponding to the axeszof the tone-arm, Such rotatory movements ;tendto develop torquef orces which, in turn, tend-s tor produce; abnormalrotae tional displacements of; the; tone-arm, with the result that. thepickupneedletends toslidei-over or-to leave thesurface of thegrecord111501516 3130 overcome these conditions; the finvehticiliprovides theunit I i with count rba an ineza fl* Q 1 T0r ta inem a s w ich ndto: uterectr hg fiects of such rotatory; movementspf the phonograph.

For the purposez of. counteracting the effectg of; those rotatorymovements which; tend tocause abnormal, displacement oh the: tone-armabout the axis,ofrotationat pivot 15, a mass, indicated generallyatfil(Figures 1.. and; 2;) and, mounted torotateat itscenter of: gravity on asupport 3.2; is so connected-withv said pivot as: to 'rotate in a;directionopposite to the-- direction in which said: Divot, tends torotate. under influence, of such rotatory movements of. thephonograph.In the embodiment illustrated,inethe drawinga the rotate able mass andits support are housed an enlarged portion 33; of the tone-armsupporting member l2; The-mass,- asshowmconsistsof; a pair of balan edvflywheels; 3d and tea, a shaft- 35 interconnectin the: fiywheels-attheir centers; and a gea 36 fix dz oh shaft; Th support: 32ineludessuitable;bearingsfi]. (Eigurejz) which-are p d: o n ag theshaft? tease. as. to. suppor sa d t-.i i hz ts gea and? flywheelsinperfectly balanced condition. 'The gear .36 engagesms ear ent .8 n cvidddnz ne end of; anarm 3.9,;the other, indi t-W i h:is' i eidir secured;.asrindicated at t-dinfligure Z'gtothepivoti 1530f the toner-arm, in,such amann r. that saidarm-.tilrcxtendsfrom said pivot and; to. heylindrical: supportin member. 2 Thefiywheelesha it a um-gear assein hlwhi h. constitut s; therotatable mass: 31 is uch: hat: its: m ment; .13nertia; about: shaft: 35; a t y dv ami al y ala cesz he moment f; in;- r-iax f the o ema emblr-ab utn vctz tfiand in lud nszthe. arm. 3 9 and: earqsesmentcfiii .1 T Thus; t mass 12p sesha endency; of? the tonearmrto, rotate aboutlthe axis; of pivot [5, when c vibrations tend to:mpartrctatorvmovements, to the phonograph; in directions correspondingto axis of; rotationalfpivot. l5;

lor: he; p pose o counteractin the; eiiect. hos rotatory Increments;Whichi end; to

cause abnormal displacement of the tone-arm about the axis of rotationalsupporting body i2, another mass, indicated generally at l I is mountedto rotate at its center of gravity and is so connected with said body asto rotate in a direction opposite to the direction in which said bodytends to rotate under influence of such rotatory movements of thephonograph. In the arrangement shown, the rotatable mass M consists of abalanced flywheel 42 and a pinion 43 rigidly connected with saidflywheel. The flywheel-andpinion assembly is rotatably suspended on astud 44 suitably attached to the lip 20 of part 18 of the ball-bearingconnection, which part is fixedly secured to base plate I. The pinion 43engages a gear-toothed element iii provided on the circumferentialsurface of enlarged portion 35 of the tone-arm supporting member 12. ThefiyWheel-and-pinion assembly constituting the rotatable mass M is suchthat its moment of inertia, about stud 44 exactly dynamically balancesthe moment of inertia of the complete tonearm assembly, about thevertical axis of member I2, including the mass 3|, connecting arm 39 andsegment 38. Thus the mass 4| opposes the tendency of the tone-arm torotate with supporting member l2 about the longitudinal axis of thelatter, when shocks or vibrations tend to impart rotatory movements tothe phonograph in directions corresponding to said axis of therotational member l2.

In associating the tone-arm mounting unit I! with the phonograph, thetone-arm supporting member [2 of said unit is introduced, as representedin Figure 13, through opening IQ of base plate 7, and is guided in saidopening until lip 26 of ball-bearing connection part It comes in contactwith the confronting side of said base plate. The nut 22 is then engagedwith threaded portion 2! of said part I8, and is tightened until theunit becomes securely clamped on the base plate. Bracket 25 is thensecured to member I2 by means of fastening element 26. The tonearm 6 maythen be rigidly connected with said member by engaging bifurcatedtrunnions 16 with pivot i5 and by tightening the fixing elements I! onsaid pivot which, in order to insure positive connection, may beprovided with suitable depressions disposed to receive the end of saidelements 11, as shown in Figure 2. When mounted, the tone-arm isaccurately balanced on its support by adjusting weight 28, if this isfound necessary. Spring 23 (Figure 1) which is adapted to supply therequired needle pressure on the record, is then connected to thetone-arm 6 and bracket 25.

From the foregoing description, it will be appreciated that the presentinvention provides a simple yet dependable arrangement whereby thetone-arm of a phonograph is capable of free normal movement during theplaying of a record, but is effectively checked against undesiredmovements, in all directions. Moreover, from the preceding descriptionit will be appreciated that the invention makes it possible to provide amounting unit for a phonograph tone-arm, which unit functions to insureproper playing of a record regardless of the position of the phonographor of any swinging or shaking motion to which the phonograph may besubjected. Particularly, the provision of a tone-arm mounting unit asherein described, has the advantage that it can be readily used toreplace the usual tone-arm support provided on phonographs, especiallybecause such a unit can be mounted without the exercise of exceptionalskill.

I claim:

1. A unit for mounting a phonograph tone-arm to rotate about twoperpendicularly related axes, said unit comprising a tone-arm supportingmember, means arranged on the supporting member to mount the same forrotation about one of said axes, a flywheel structure supported by saidmeans to rotate in aplane transverse to said one axis and connected withsaid member for rotation counter to the rotation of the latter, atone-arm engaging element mounted on said member for rotation therewithabout said one axis and for rotation relative to said member about theother of said axes, and a second flywheel structure supported by saidmember to rotate in a plane transverse to said other axis and connectedwith said element for rotation counter to the rotation of the latter.

2. A unit as set forth in claim 1, in which the supporting member ishollow, the first-mentioned flywheel structure is supported exteriorlyof said member by the stated means, and the second-mentioned flywheelstructure is supported interiorly of and by said member.

3. A tone-arm mounting unit comprising a generally cylindrical member,support means arranged on said member to mount the same for rotationabout its longitudinal axis, a flywheel structure supported by saidmeans to rotate about an axis substantially paralleling the mentionedrotational axis of said member, a connection between said member andflywheel structure to rotate the latter counter to the rotation of saidmember, a rotatable shaft provided on said member and extending in aplane transverse to the rotational axis of said member and adapted forconnection with a tone-arm, said shaft being arranged for rotation withsaid member and for rotational movement with respect thereto about anaxis extending substantially at right angles to the rotational axis ofsaid member, a second flywheel structure housed and supported withinsaid member to rotate about an axis substantially paralleling saidshaft, and a connection between said shaft and second flywheel structureto rotate the latter counter to the rotation of said shaft.

4. A tone-arm mounting unit as set forth in claim 3, in which thefirst-mentioned connection includes a pinion attached to thefirst-mentioned flywheel, and a toothed wheel afiixed to the generallycylindrical member and in mesh with said pinion; and thesecond-mentioned connection includes a gear as part of the secondflywheel structure, and an arm secured to the rotatable shaft and havinga toothed rack in mesh with said gear.

ELMER O. THOMPSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,033,729 Montfort Mar. 10, 19362,263,979 Bruno Nov. 25, 1941 2,331,122 Jones Oct. 5, 1943

